Your father's symptoms?severe back pain radiating down his right leg with difficulty standing?strongly suggest sciatica or a pinched nerve in the spine. He needs an urgent medical evaluation. Avoid starting strong prescription medications without a proper diagnosis. For temporary relief, he may take over-the-counter pain relievers like Acetaminophen (Tylenol) or Ibuprofen, if medically safe for him. Applying a cold or warm compress may also help. Please consult a physician promptly for a physical exam. Seek immediate emergency care if he experiences sudden leg weakness, numbness in his groin area, or loss of bowel or bladder control.